Expandable threaded arcuate interbody spinal fusion implant with lordotic configuration during insertion

ABSTRACT

An at least in part frusto-conical threaded interbody spinal fusion implant having an expandable height.

BACKGROUND OF THE INVENTION

This is a continuation of U.S. application Ser. No. 09/574,858, filedMay 19, 2000; which claims the benefit of U.S. Provisional ApplicationNo. 60/180,404, filed Feb. 4, 2000; all of which are incorporated byreference herein.

FIELD OF THE INVENTION

The present invention relates generally to an improved interbody (forplacement at least in part between adjacent vertebral bodies) threadedspinal fusion implant for the immobilization of vertebrae. The presentinvention is directed to threaded implants only and not to non-threadedimplants. In particular, the invention relates to a threaded spinalfusion implant that is selectively directionally expandable and whichspecifically has height raising capabilities that are utilized once theimplant is initially positioned. More particularly, the inventionrelates to a threaded implant having arcuate portions of upper and lowermembers that in a first, collapsed, or insertion position are angled toone another and form at least a portion of a frusto-conical shape alonga substantial portion of the length of the implant.

DESCRIPTION OF THE RELATED ART

Threaded spinal fusion implants are known in the related art. The firstartificial threaded spinal fusion implant was invented by Michelson andis disclosed in U.S. Pat. No. 5,015,247, which is hereby incorporated byreference.

Lordotic, frusto-conical, or tapered, threaded-spinal fusion implantsare also known in the art. By way of example, Michelson has inventedsuch implants as disclosed in U.S. application Ser. No. 08/480,904,which is hereby incorporated by reference.

Expandable fusion implants are known in the related art. The firstexpandable spinal fusion (allowing for the growth of bone from vertebralbody to vertebral body through the implant) implant was invented byMichelson and is disclosed in U.S. Pat. No. 5,776,199, which is herebyincorporated by reference.

Lordotic, frusto-conical, or tapered, spinal fusion implants have theadvantage of restoring or enhancing spinal lordosis. Threaded spinalfusion implants offer the advantage of being easily positioned in theimplantation space and of having excellent fastening or holdingfeatures. Expandable fusion implants offer the advantage of allowing forthe placement of a potentially larger implant through a smaller openingin a patient's body. Selective expansion along a single direction, (e.g.vertical only when correctly installed) offers the advantage ofincreasing the height of the implant and therefore the distraction ofthe disc space, but without a concomitant increase in the width of theimplant.

There exists a need for an artificial interbody spinal fusion implantproviding for all of the aforementioned advantages in combination.

SUMMARY OF THE INVENTION

In accordance with the present invention, as embodied and broadlydescribed herein, there is provided an expandable threaded artificialinterbody spinal fusion implant, having a shape that is generallyfrusto-conical when inserted, for insertion across a disc space betweentwo adjacent vertebral bodies of a human spine. The threaded implant ofthe present invention includes an upper member having an arcuate portionadapted for placement toward and at least in part within one of theadjacent vertebral bodies and a lower member having an arcuate portionadapted for placement toward and at least in part within the other ofthe adjacent vertebral bodies. The arcuate portions of the upper andlower members have at least one opening in communication with oneanother for permitting for the growth of bone from a vertebral body toan adjacent vertebral body through the implant. The upper and lowermembers are articulated therebetween, preferably proximate one of theproximal ends and the distal ends of the upper and lower members andpreferably allow for divergence between the articulating members at theend opposite the articulating end of the implant. The upper and lowermembers have a first position relative to one another that allows for acollapsed implant height and a second position relative to one anotherthat allows for an increased height. The arcuate portions of the upperand lower members in the first position of the present invention areangled to one another and form at least a portion of a frusto-conicalshape along the length of the implant. A portion of at least one helicalthread is on the exterior of each of the opposed arcuate portions of theupper and lower members for engaging the adjacent vertebral bodies. Theupper and lower members have a leading or distal end, an oppositetrailing or proximal end, and a length therebetween. A blocker that ispreferably in the form of an expander is located proximate at least oneof the ends for holding at least a portion of the upper and lowermembers apart so as to maintain the increased height of the implant andresist the collapse of the implant to the collapsed implant height.Expansion of the implant preferably increases the implant height only,that is in a plane passing through the mid-longitudinal axis of theimplant and the upper and lower members.

The blocker need not be in contact with the upper and lower members whenthe implant is initially inserted into the implantation space. Theblocker may be a block or any type of spacer that is inserted between orotherwise holds apart the articulated upper and lower members after theimplant is positioned so as to hold portions of the upper and lowermembers spaced apart the optimal height and angulation relative to oneanother. That is, the implant may be expanded with an extrinsic tool andthen the expanded portions held apart in the second position by a thirdbody blocker or blockers placed therebetween. Further, a physician maybe able to select from a series of blockers having different heightsusable with the same implant. The present invention includes expandingthe implant with a tool, such as a spreader or a distractor, but is notlimited to a scissors type, a rack and gear type, a threaded member typeor any other type of particular external expander tool mechanism. Eachtool nevertheless preferably engages the upper and the lower implantmembers to urge the implant apart. Then the blocker may be inserted intocontact with the upper and lower members to maintain the implant at anexpanded height. The height of the gap created by expanding the implantmay be measured so that the appropriately sized blocker or expander maybe inserted into contact with the upper and lower members depending uponthe amount of distraction of the implant desired by the physician.

In a preferred embodiment, the blocker is in contact with the upper andlower members prior to the implant expansion; and the blocker is itselfthe expander, which may be operated by an extrinsic tool. By way ofexample only, the expander may rotate: to increase the height of theimplant; in a single direction; more than 40 degrees and less than 140degrees and more preferably approximately 90 degrees to move from afirst insertion position to a second/deployed position; and in a planeperpendicular to the longitudinal axis of the implant to increase theheight of the implant. The expander preferably remains in the sameperpendicular plane relative to the longitudinal axis of the implantwhen rotated. In another embodiment the expander may be a member, suchas a plate, a rod, or of any other configuration suitable for theintended purpose initially within the interior between the upper andlower members in a collapsed position that is erected to a more erectposition when the implant is in the expanded position. The expander canbe hollow or solid.

In a preferred embodiment, the expander preferably has means including,but not limited to, an opening, a projection, or a detent adapted tocooperatively engage a tool used to rotate the expander to increase theheight of the implant. The opening, projection, or detent is adapted tocooperatively engage a tool that preferably rotates about an axisparallel to the longitudinal axis the implant to rotate the expander toincrease the height of the implant. Rather then having an opening, aprojection, a detent, or a central aperture, the expander may have twoor more recesses or holes placed on or through the proximal face toengage a tool. In an alternative embodiment of the expander, cutouts maybe positioned along a portion of the perimeter of the expander.

The expander is preferably located proximate at least one of theproximal end or the distal end of the upper and lower members. Theexpander, however, need not be so located. The expander may be spacedaway from the end and even permit a hollow portion to exist on both theproximate and distal sides of the expander. The upper and lower memberspreferably have an interior surface therebetween and a hollow definedtherein with the expander located proximate one of the longitudinal endsof that interior hollow. The hollow between the ends of the upper andlower members is preferably unobstructed by the expander so as to permitgrowth of bone directly through the hollow unobstructed by the expanderfrom vertebral body to vertebral body through the implant transverse tothe longitudinal axis of the implant. The implant may comprise a secondand lesser hollow extending at least in part from the expander to theend of the upper and lower members proximate that expander. A preferredexpander mechanism includes an expander in combination with cooperatingsurfaces of the end wall of the implant that guide and support theexpander.

Preferred forms of interbody spinal fusion implants have a substantialhollow portion. Certain expandable interbody spinal fusion implants thatincrease in height only of the related art contain an expansionmechanism passing longitudinally therethrough or an expansion mechanismthat is configured for movement of the expansion mechanism fromproximate one end of the hollow portion to proximate the other end ofthe hollow portion, thus requiring the expander to pass through thelength of the hollow portion. A preferred embodiment of the presentinvention overcomes these limitations.

The expander moves the arcuate portions of the upper and lower membersfrom an angled orientation to a parallel orientation relative to oneanother; from a first angled orientation to a second angled orientationrelative to one another; or from a first height at each end to a secondand greater height at at least one and possibly both ends, but in eachevent the arcuate portions of the upper and lower members in the firstor insertion position are angled to one another over a substantialportion of the length of the implant, and/or form at least a portion ofa frusto-conical shape along the length of the implant. Each of theupper and lower members may structurally cooperate with a blocker, orexpander so as to keep it located so as to function for its intendedpurpose. By way of example, each of the upper and lower memberspreferably has a track within which the blocker may be captured or theexpander rotated. The tracks may be configured to permit the expander torotate therein and then to move from side to side therewithin. The trackof the upper member and the track of the lower member are preferably inthe same plane and the plane is preferably perpendicular to thelongitudinal axis of the implant.

A preferred expander has a first height in a first or insertion positionand a greater second height when rotated or positioned into a second ordeployed position to increase the maximum height of the implant from afirst maximum height to a second maximum height. By way of example, atleast one of the tracks of the upper and lower members preferably has acooperating surface and the expander has a corresponding cooperatingsurface that contacts the cooperating surface of the track to orient theexpander in a predetermined position. The cooperating surfacespreferably orient the expander within the implant such that the axis ofrotation of the expander is parallel with the longitudinal axis of theimplant and, more preferably, center the expander within the implantsuch that the axis of rotation of the expander coincides with thelongitudinal axis of the implant. As may be advantageous for the furtherloading of the implant with fusion-promoting material, the expander maycooperate with the tracking surfaces of the upper and lower members toallow the expander to slide from side-to-side for easier access to theimplant interior.

The implant is preferably packed full of bone or other fusion-promotingsubstances prior to expansion of the implant. Expansion of the implantresults in a space being formed in the implant interior into whichadditional fusion promoting substances such as bone may preferably bepacked. Rotating the expander within the implant causes a void that canbe filled with bone. If the expander is configured to permitside-to-side movement, then packing of additional bone into the implantis easy.

When installing a preferred implant from the posterior approach to thespine, the implant is driven from the trailing end and the expander isat the leading end at the anterior aspect of the spine. When expanded,the implant installed from the posterior aspect leaves a void at theleading end of the implant near the anterior aspect of the spine becausethe leading end of the implant has been made taller, the void ispreferably packed with bone. Additionally, the path left behind in thebone filled interior of the implant by the tool used to access theexpander through the bone filled interior to position the expander ispreferably packed with bone as well.

In a preferred embodiment of the present invention, the expander heightchange from the first position to the second position corresponds tosubstantially the same change in height of the implant along at least aportion of the length of the implant. The expander may be configured indifferent ways. A preferred configuration for a rotational expanderincludes: a first dimension corresponding to the width of the expanderwhen the implant is initially inserted into the spine and to the heightof the rotational expander when the rotational expander is rotated toincrease the height of the implant; and a second dimension correspondingto the height of the expander when the implant is initially insertedinto the spine and to the width of the expander when the expander isrotated to increase the height of the implant. The first dimensionpreferably is greater than the second dimension.

The expander may have an upper surface, a lower surface, and sidesurfaces as defined when the expander is positioned after rotation toincrease the height of the implant. As used herein, the term “sidesurfaces” refers to those portions of the expander that extend from theupper member to the lower member after the expander has been rotatedinto its second or deployed position to increase the height of theimplant. The “upper” and “lower” expander surfaces refer to thoseportions of the expander that are in contact with the upper and lowermembers when the implant is in its second or expanded configuration.Each of the upper and lower surfaces of the expander may lie generallyin a plane and may be generally parallel to one another. The sidesurfaces and the upper and lower surfaces may be oriented so as tosubstantially form a parallelogram, which will typically be in the shapeof a rectangle generally.

A preferred expander is in the form of a modified rectangle or rhomboid.The expander generally has a longer dimension and a shorter dimension.When the expander is in a first position, the short dimension spans thedistance between the upper and lower members and when the expander is inthe second position, the expander's long dimension spans the distancebetween the upper and lower members.

The expander may have a cross-section with the side surfacesintersecting the upper and the lower surfaces at junctions, which may betwo diametrically opposed corners and two diametrically opposed arcs.The two diametrically opposed arcs may be each of the same radius and,preferably, the diagonal or modified hypotenuse “MH” between the opposedarcs has a maximum dimension that generally approximates the distancebetween the upper and lower surfaces such that, when the expander isrotated from a first insertion position toward a second/deployedposition, no substantial over-distraction occurs between the adjacentvertebral bodies as would occur if the height of the implant wasincreased markedly beyond that obtained in the second/deployed position.The two diametrically opposed corners may form a 90-degree angle. Theexpander preferably has a fixed shape during movement from a firstinsertion position to a second/deployed position within the implant.

In a preferred embodiment, a modified hypotenuse or diagonal “MH” is thedimension between the two diametrically opposed arcs that allows for therotation of the expander from a first position to a second positionwithout substantial over-distraction occurring during this process. Thephrase “without substantial over-distraction” is defined as distractingthe vertebral bodies in the range of elastic deformation and short ofplastic deformation and tissue failure. To avoid any ambiguity regardingthe phrase “without over-distraction,” this phrase and the individualwords contained therein are not being used as they may be in theirnormal or ordinary use, but are being used as defined in thisapplication only. In the example of this rotational expander, the MHcould be identical in length to the height thereby assuring literally nooverdistraction. It may be preferred, however, to have the MH justslightly greater in length than the height to insure the stability ofthe expander in the expanded or second position because this would thenrequire additional force over the stable position to derotate theexpander.

In accordance with an embodiment of the present invention, a secondexpander may be located between the upper and lower members for movingat least a portion of the upper and lower members away from one anotherto increase the height of the implant as defined by the maximum distancebetween the arcuate portions of the upper and lower members proximatethat expander. All of the features described herein for the expander mayalso be applicable to the second expander. Additionally, the secondexpander may be located proximate an end of the implant opposite theother expander, thereby providing an implant capable of being expandedat both ends of the implant. The increased height of the implantresulting from moving the two expanders may be constant or varied alongthe length of the implant according to the desired configuration of theimplant and the relative dimensions of the individual expanders. A givenimplant may be adapted to receive or cooperatively engage a series ofprogressively sized (taller) blockers or expanders to allow the surgeonto make a final height selection at the time of surgery.

In accordance with an embodiment of the present invention, the implantmay include an expansion mechanism including the expander and at leastone partial wall structure preferably located proximate an implant endthat guides and holds the expander in a predetermined position.

The implant may have an overlapping step-cut wall junction between theupper and lower members, which offers as some of its advantages:increasing the lateral rigidity of the implant, holding the implant inthe closed first position until expanded, and to the extent desiredretaining the fusion-promoting materials within the implant. The walljunction may be either solid or perforated.

One of the upper and lower members preferably has an interior wallextending toward the other of the upper and lower members and, morepreferably, has two interior walls extending from each side of thearcuate portion. The interior walls may be aligned parallel with thelongitudinal axis of the implant. The other one of the upper and lowermembers preferably has an interior-contacting surface adapted to contactor receive the interior longitudinal wall.

By way of example, one of the upper and lower members may have alongitudinally extending interior wall, which is preferably unexposed,extending toward the other of the upper and lower members when theimplant is in an initial insertion position. When the implant is in thefinal expanded or deployed position the implant has a preferred shapesuch that each of the arcuate portions of the upper and lower membersare separated by at least a portion of interior wall, which in thisposition preferably has an exposed side.

The upper and lower members in certain embodiments are articulated toone another so one of the respective ends of the upper and lower membersremain articulated while the other of the respective ends of the upperand lower members are free to move away from one another. In a preferredembodiment, the articulating means is achieved without a third member,such as an axle shaft, for example, passing through the implant. Thearticulating means preferably is formed into the implant wallsthemselves, and in a further preference in such a way that thetwo-implant halves may be articulated when at 90 degrees to each other.The halves then are moved, much like a book closing, toward each otherprior to insertion into the implantation space in the spine. Once theupper and lower members are closed from the approximately 90 degreesarticulating position, much like closing the leaves of a book, the upperand lower members of the implant are locked together at the articulationso that the members will not disarticulate when in use. Other types ofarticulation as would be known to one of ordinary skill in the art arewithin the scope of the present invention.

By way of example, the upper and lower members preferably have acooperating rotational articulation or pivot point between a proximateone of the proximal end and the distal end of the upper and lowermembers. The cooperating rotational articulation preferably is proximateone of the proximal end and the distal end of the upper and lowermembers at an end opposite the expander when only one end is to beexpanded. A preferred rotational articulation configuration includescooperating brackets and projections configured such that articulationtherebetween occurs when the upper and lower members are substantiallyperpendicular to one another. Such a configuration offers the advantagethat the brackets and the projections will not disengage one anotherwhen articulated for use such as insertion into the spine and subsequentexpansion within a range of movement of the upper and lower membersresulting from the expander positioning.

When the implant is in the final or expanded position the implant maytake the general form of a frusto-conical shape split along a horizontalplane through its mid-longitudinal axis wedged upper half from lowerhalf by an inclined plane.

At least one and preferably both of the upper and lower members may havea screw hole passing through the trailing end, which preferably isadapted to receive a screw passing through the end of the upper andlower members and from the interior of the implant into each of theadjacent vertebral bodies to anchor the implant, further stabilize thosevertebral bodies relative to each other, prevent undesirable motion atthe vertebral body implant interfaces, increase the compressive load atthe implant trailing end, prevent rocking and thereby to mitigateagainst excessive peak loads, and to more uniformly distribute loadsimparted to the implant over the length of the implant to the adjacentvertebral bodies. The implant may have a side configured, when in theexpanded position, to cooperate with another interbody spinal fusionimplant so as to allow the pair of implants to have a reduced combinedwidth.

The trailing end of the implant preferably has a tool-engaging portion,but the implant may be adapted to cooperatively engage a driver atanother location or by any means as would be known to one of ordinaryskill in the art. This tool-engaging portion is adapted to engage aninsertion tool that holds and rotates the implant into position. Theconfiguration of the tool-engaging portion may be an opening, and moreparticularly an opening that is along the longitudinal axis of theimplant to facilitate the use of an insertion tool that rotates theimplant into an inserted position. It is appreciated that thetool-engaging portion need not be an opening. A hole or a blind hole,threaded or otherwise, is preferred in another embodiment. In anotherpreferred embodiment the opening preferably is a threaded slot thatfunctions to cooperatively engage and disengage a tool for use ininserting the implant. In specific embodiments, the leading or trailingend may have wall portions, and/or be adapted to cooperatively engage acap. Either the end wall portions or a cap may have an opening oropenings, which may function to hold fusion-promoting materials withinthe implant and/or, permit vascular access and bone growth therethrough.

For an embodiment of an implant of the present invention having oneexpander, the main access opening is preferably at the end opposite fromthe expander. The main opening may be at either the distal or proximalend of the implant. The end of the upper and lower members containingthe expander may serve as a secondary access opening.

By way of example, an implant configured for insertion from an anteriorapproach may be initially packed from the distal or leading end of theimplant. The implant is then driven into position. Once the expander ismoved into final position and any associated tool for positioning theexpander is withdrawn from the expander, any void in the bone packedinto the implant interior may be filled. The expander may be moved fromside-to-side to pack more bone into the implant. In essence, theside-to-side movement of the expander provides for a secondary accessopening for accessing the hollow interior of the implant and forcompressively loading it with fusion-promoting substances. Theaccompanying drawings, which are incorporated in and constitute a partof this specification, are by way of example only and not limitation,and illustrate several embodiments of the invention, which together withthe description, serve to explain the principles of the invention. Thescope of the invention is limited only by the scope of the claims asfrom the present teachings other embodiments of the present inventionshall be apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a spinal fusion implant of oneembodiment of the present invention;

FIG. 1A is a perspective view of an alternative embodiment of a blockerin the form of an expander for use with the spinal fusion implant ofFIG. 1;

FIG. 1B is a perspective view of another alternative embodiment of ablocker for use with the spinal fusion implant of FIG. 1;

FIG. 1C is a perspective view of yet another alternative embodiment of ablocker for use with the spinal fusion implant of FIG. 1;

FIG. 2 is a top plan view of the implant of FIG. 1;

FIG. 3 is a trailing end view of the implant of FIG. 1;

FIG. 4 is a side elevation view of the implant of FIG. 1;

FIG. 5 is a leading end view of the implant with the end cap thereattached of FIG. 1;

FIG. 6 is a cross-sectional view along line 6-6 of FIG. 2;

FIG. 7 is a cross-sectional view along line 7-7 of FIG. 5;

FIG. 8 is a side elevation view of an end cap for use with the implantof FIG. 1;

FIG. 9 is a schematic representation of a geometric configuration of across-section of an expander in accordance with one embodiment of thepresent invention;

FIG. 10 is a trailing end perspective view of the implant of FIG. 1;

FIG. 11 is a side view of the implant of FIG. 10 being inserted from agenerally anterior approach to the spine into an implantation siteformed across a disc space and two adjacent vertebral bodies of thespine shown in partial cross-section;

FIG. 12A is a cross-sectional view of the implant of FIG. 1 inserted inan implantation site formed across the disc space and two adjacentvertebral bodies of the spine;

FIG. 12B is a cross-sectional view of the implant of FIG. 1 inserted inan implantation site of FIG. 12A and expanded to place the adjacentvertebral bodies in proper lordosis;

FIG. 12C is a trailing end perspective view of the implant of FIG. 1with the implant in an expanded position;

FIG. 13 is a trailing end view of the anterior aspect of two adjacentvertebral bodies and two implants of FIG. 1 implanted therebetween in afinal position;

FIG. 14 is a cross-sectional side view of an implantation site formedposteriorly across the disc space between two adjacent vertebral bodiesand a second embodiment of an implant of the present invention forposterior insertion being installed into the implantation site;

FIG. 14A is a side view of an alternative variation of a secondembodiment of the implant of FIG. 14 for posterior insertion;

FIG. 15 is a cross-sectional side view of the implantation site formedacross the space between two adjacent vertebral bodies and the implantof FIG. 14 installed into the implantation space;

FIG. 16 is a leading end perspective view of the implant of FIG. 14;

FIG. 17 is a top plan view of another embodiment of the presentinvention inserted upon the lower vertebral body of an implantation siteformed anteriorly across a disc space with the vertebral body shown inpartial cross-section;

FIG. 18A is a cross-sectional side view of the implantation site formedacross the space between two adjacent vertebral bodies and one of theimplants of FIG. 17 installed into the implantation space;

FIG. 18B is a trailing end view of the anterior aspect of two adjacentvertebral bodies and the implant of FIG. 17 implanted therebetween in anexpanded position as well as another embodiment designed to be used as aside-by-side pair;

FIG. 19 is a cross-sectional side view of the implant of FIG. 18Awithout bone or other fusion-promoting substances shown therein for thepurpose of illustrating a preferred configuration for articulating theupper and lower members together with a hook and peg configuration thatprevents the implant from over expanding and with an alternative secondhook and peg shown on the right hand side of the figure in dashed lines;

FIG. 20 is a partial cross sectional view of an embodiment of aninterlocking wall design along line 21-21 of FIG. 19;

FIG. 21 is a partial cross sectional view of another embodiment of aninterlocking wall design along line 21-21 of FIG. 19;

FIG. 22A is a cross-sectional side view of an alternative embodiment ofan implant of the present invention with a pivoting trailing end that isalso a blocker in the trailing end in the open position;

FIG. 22B is a cross-sectional side view of an alternative embodiment ofan implant of the present invention with a pivoting trailing end that isalso a blocker with the trailing end in the closed position; and

FIG. 23 is a trailing end perspective view of the implant of FIG. 22B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is intended to be representative only and notlimiting and many variations can be anticipated according to theseteachings, which are included within the scope of this inventiveteaching. Reference will now be made in detail to the preferredembodiments of this invention, examples of which are illustrated in theaccompanying drawings.

Shown in FIGS. 1-7 and 10-13, in accordance with the present invention,as embodied and broadly described herein, is one embodiment of anexpandable threaded artificial interbody spinal fusion implant 100 foranterior insertion across a disc space D between two adjacent vertebralbodies V of a human spine. Threaded implant 100 of the present inventionincludes an upper member 102 having an arcuate portion 104 adapted forplacement toward and at least in part within the upper of the adjacentvertebral bodies V and a lower member 106 having an arcuate portion 108adapted for placement toward and at least in part within the lower ofthe adjacent vertebral bodies V. Arcuate portions 104, 108 of upper andlower members 102, 106 have at least one opening 110, 112 incommunication with one another for permitting for the growth of bonefrom vertebral body V to adjacent vertebral body V through implant 100.Upper and lower members 102, 106 are articulated therebetween at anadjacent one of the proximal ends and the distal ends of upper and lowermembers 102, 106 and allow for rotation between the articulating membersat the end opposite the articulating end of implant 100. Upper and lowermembers 102, 106 have a first position relative to one another thatallows for a collapsed implant height and a second position relative toone another that allows for an increased height. Arcuate portions 104,108 of upper and lower members 102, 106 in the first position of thepresent invention are angled to one another and form at least a portionof a frusto-conical shape along the length of implant 100. A portion114, 116 of at least one thread 118 is on an exterior 120 of each ofopposed arcuate portions 104, 108 of upper and lower members 102, 106for engaging adjacent vertebral bodies V.

While a specialized form of a blocker 121 is described in significantdetail below with reference to expander 122, blocker 121 need not be incontact with upper and lower members 102, 106 when implant 100 isinitially inserted into the implantation space. Blocker 121 may be ablock or any type of spacer that is inserted between the articulatedupper and lower members 102, 106 after implant 100 is positioned so asto hold portions of the upper and lower members 102, 106 spaced apartthe optimal height and angulation relative to one another. That is, theimplant may be expanded with an extrinsic tool and then the expandedportions held apart in the second position by a third body blockerplaced therebetween. Further, a physician may be able to select from aseries of blockers having different heights usable with the sameimplant. The present invention includes expanding the implant with atool, such as a spreader or a distractor but is not limited to ascissors type, a rack and gear type, a threaded member type or any otherspecific type of movement mechanism. Each tool nevertheless preferablyengages upper and lower implant members 102, 106 to urge them apart.Blocker 121 is then inserted into contact with upper and lower members102, 106 to maintain implant 100 at an expanded height. The height ofthe gap created by expanding implant 100 may be measured so that theappropriately sized blocker 121 or specialized blocker, expander 122,may be inserted in implant 100 depending upon the amount of distractionof implant 100 desired by the surgeon.

Blocker 121 that is preferably in the form of expander 122 is locatedproximate at least one of the ends of the implant upper and lowermembers 102, 106 and holds at least a portion of upper and lower members102, 106 apart so as to maintain the increased height of implant 100 andresist the collapse of implant 100 to the collapsed implant height.Expander 122 in the present embodiment increases the implant height asmeasured in a plane passing through the mid-longitudinal axis of implant100 and upper and lower members 102, 106 during positioning of expander122 and as may be desirable is capable of selectively increasing theheight of the implant only.

Expander 122 in the present embodiment is adapted to rotate in a singledirection approximately 90 degrees to move from an initial (first)insertion position 1, as best shown in FIGS. 1, 3 and 10, to a final(second) deployed or expanded position F, as best shown in FIG. 13, toincrease the maximum height H of implant 100. Expander 122 preferablyrotates in a plane perpendicular to the longitudinal axis L of implant100 to increase the maximum height H of implant 100. During rotation,expander 122 remains in the same perpendicular plane relative to thelongitudinal axis L of the implant. It is appreciated that an expanderwithin the scope of the present invention may be designed to: rotate ineither direction or both directions; rotate more than 40 degrees andless than 140 degrees; rotate more or less than 90 degrees; or rotate ina plane other than perpendicular.

Expander 122 has an opening 124 adapted to cooperatively engage a tool(not shown) used to rotate expander 122 to increase height H of implant100. Opening 124 is adapted to cooperatively engage a tool thatpreferably rotates about an axis parallel to the longitudinal axis L ofimplant 100 to rotate expander 122 to increase height H of implant 100.Opening 124 also may be used as a passageway to pass fusion-promotingsubstances through expander 122 and into implant 100. It is appreciatedthat the expander may also include a projection, a detent, or any otherconfiguration in place of or in addition to an opening so as tocooperatively engage a tool to move the expander.

In an alternative embodiment, an expander 122′ could have cutouts alongany portion of its perimeter not involved in the actual rotation asshown in FIG. 1A. In another alternative embodiment, a blocker 121having cutouts along a portion of its perimeter can be positioned intothe implant as shown in FIG. 1B. The cutouts can be used to engage araised area within the implant to lock blocker 121 or expander 122′ intoposition or be used by the surgeon to grasp blocker 121 with a tool thatcooperatively engages the cutouts to facilitate inserting blocker 121into the implant. Rather then having an opening, a projection, a detent,or a central aperture, a blocker 121′ alternatively could have two ormore recesses or holes placed on or through the proximal face to engagea tool as shown in FIG. 1C.

As shown in FIGS. 1, 6, 7, 10, 12A-12C, and 13, in one preferredembodiment of the present invention for anterior insertion, expander 122is located proximate the trailing end 126 of upper and lower members102, 106. While in a second embodiment as shown in FIGS. 14-16 forposterior insertion, expander 222 is located proximate the leading end250. As shown if FIGS. 17-19, in third and fourth embodiments of thepresent invention for anterior insertion and possible use together,expanders 322 are located proximate each of leading and trailing ends330, 326 of implants 300.

Implant 100 preferably has an interior surface 128 and a hollow 130defined therein. Expander 122 of the present embodiment is locatedproximate interior surface 128 and more particularly proximate interiorsurface 128 at trailing end 126 of upper and lower members 102, 106. Asis preferred, hollow 130 between the ends is unobstructed by expander122 so as to allow for the unimpeded loading of the interior of theimplant with the desired fusion-promoting substances; thus, loading theimplant is easy. Further, this preferred configuration of implant 100makes available all of the volume of the hollow to containfusion-promoting substances and so as to permit for the growth of bonedirectly through the hollow unobstructed by the expander to adjacentvertebral bodies V. Unobstructed hollow 130 further allows for packingimplant 100 with fusion-promoting substances. It is appreciated thatdepending on the intended results, the expander also may be located atdistal end 126 or leading end 150 of upper and lower members 102, 106 oranywhere else within the implant. The unobstructed hollow preferably hasno mechanism extending along the longitudinal axis of the implant whenfinally deployed and the mechanism that moves the implant from a firstposition to a second position preferably does not move expander 122longitudinally through the hollow portion. The expander may work bypivoting on a surface in contact with an interior wall portion of atleast one of the upper and lower members 102, 106. Moreover, multipleexpanders may be used in contact with upper and lower members 102, 106at any location within the implant.

An alternative embodiment of an expander used with the present inventionincludes an expander having an external thread that cooperates withconverging threaded portions of the upper and lower members 102, 106 toexpand the implant as the expander is rotated into position. Anotheralternative embodiment of an expander includes an expander having a camconfiguration to expand the implant upon rotation.

The mechanism or tool used to move the expander is not part of theimplant itself as the mechanism or tool is removed from the implant uponmoving the expander, e.g. such as to rotate it into place and thusexpand the implant to the final expanded position.

Expander 122 of the present embodiment moves arcuate portions 104, 108of upper and lower members 102, 106 from a first angled orientation A,as shown in FIGS. 1 and 11 in a first position, to a second angledorientation A′, as shown in FIG. 12B where implant 100 has a generallyoblong cross section at trailing end 126, in a second position. Theimplant of the present invention need not be a true frusto-conical shapeas a cross section need not form a complete circle but may have portionsof the perimeter absent, less round, flattened including flattened ontwo or more sides, or other. It is appreciated that the expander alsomay move the arcuate portions of the upper and lower members from afirst height at each end to a second and greater height at each end.

In this embodiment, each of upper and lower members 102, 106structurally cooperate with expander 122 so as to keep it located so asto function for its intended purpose. Each of upper and lower members102, 106 of the implant of FIG. 1 has a track 132, 134 within whichexpander 122 rotates. As best shown in FIGS. 1 and 13, track 132, 134 isconfigured to permit expander 122 to rotate therein and then to movefrom side to side within track 132, 134. Track 132 of upper member 102and track 134 of lower member 106 are in the same plane and the plane isperpendicular to the longitudinal axis of implant 100. It is appreciatedthat the track of the upper and lower members may be in differentplanes. Such a track design may be used with an expander with a step init or with offset tabs to engage tracks in different planes than oneanother. As with the expander, the tracks also may be at various anglesto the longitudinal axis of the implant including parallel with thelongitudinal axis of the implant. Other means for respectively engagingthe implants and the expander position thereof are anticipated andwithin the scope of the present invention.

In rotating the expander, the longer dimension of the expander issubstituted for the lesser dimension of the expander thuscorrespondingly increasing the maximum height of the implant from thefirst to the second position. As best shown in FIG. 9, the schematicrepresentation of a geometric configuration of a cross-section of anexpander 122 in accordance with one embodiment of the present invention,includes: a first dimension X corresponding to the height of expander122 when implant 100 is initially inserted into the spine and to thewidth of expander 122 when expander 122 is rotated to increase height Hof implant 100; and a second dimension Y corresponding to the width ofexpander 122 when implant 100 is initially inserted into the spine andto the height of expander 122 when expander 122 is rotated to increaseheight H of implant 100. Second dimension Y is greater than firstdimension X. Expander 122 has an upper surface 136, a lower surface 138,and side surfaces 140 as defined when expander 122 is positioned afterrotation to increase height H of implant 100. As used herein, the term“side surfaces” refers to those portions of expander 122 that extendfrom upper member 102 to lower members 106 after expander 122 has beenrotated into its final deployed, or second position to increase theheight H of implant 100. The “upper” and “lower” surfaces refer to thoseportions of expander 122 that are in contact with upper and lowermembers 102, 106 when implant 100 is in its second position andconfiguration and is fully expanded.

A preferred expander 122 is in the form of a modified rectangle orrhomboid. The expander generally has a longer dimension Y and a shorterdimension X. When the expander is inserted into a first position, theshort dimension X spans the distance between upper to the lower members102, 106 and when expander 122 is in the second position, the longerdimension Y of expander 122 spans the distance between upper and lowermembers 102, 106.

Expander 122 in one embodiment of the present embodiment has across-section with side surfaces 140 intersecting upper and lowersurfaces 136, 138 at two junctions which may be diametrically opposedcorners 142 and two diametrically opposed arcs 144. Arcs 144 arepreferably each of the same radius and the modified hypotenuse MHbetween opposed arcs 144 generally approximates the distance betweenupper and lower surfaces 136, 138 such that, when expander 122 isrotated from an initial insertion position toward a final deployedposition, no substantial over-distraction occurs between adjacentvertebral bodies V.

The modified hypotenuse MH of this embodiment of the present inventionmay be equal, slightly less than, or slightly greater than dimension Yof expander 122. Having the modified hypotenuse MH be slightly greaterthan the dimension Y offers the advantage of having expander 122stabilized by an over-center position, such that more energy would berequired to derotate the expander than for it to remain in the deployedor second position. By “without substantial over-distraction” what ismeant is that the modified hypotenuse MH length is closer to theexpander dimension Y than to the unmodified hypotenuse UH; and isselected to allow the implant to preferably operate in the range ofelastic deformation of the tissues about the operated disc space.Corners 142 may form, but not necessarily, a 90-degree angle and have anunmodified hypotenuse dimension UH.

By way of example, consider one embodiment of expandable implant 100 ofthe present invention having an optimum expanded height of 18 mm for agiven implantation space. Any implant bigger than 18 mm should not beused in this implantation space because during expansion of the implant,its height would move through the range of elastic deformation of thesurrounding tissues and after that, the implant would crush thevertebral bone or tear ligaments. Inserting an expander such that whenthe implant is fully expanded allows the implant to be 18 mm would beideal. It may be that an implant having a 17.5 mm expanded height forthis implantation space is nearly as good, but a 16 mm expanded heightmay be too short to fit tightly within the implantation space. Using apreferred rectangular expander without any modification to thehypotenuse that is adapted to expand the implant to the optimum 18 mmfinal height would require the expander to have a hypotenuse causing theimplant to exceed the 18 mm expanded height temporarily during rotationof the expander. So turning the expander without a modified hypotenusewould break the vertebrae or tear the ligaments. In reverse, if onecould not expand the implant to more than 18 mm without causing damageto the spine, then an implant selected to have an expander having a fullunmodified hypotenuse so as to upon rotation temporarily cause theimplant height to be 18 mm would in the finally expanded position allowthe implant height to collapse such that there would be insufficientheight for the implant to adequately distract the implantation space.Generally, the modified hypotenuse of the expander is closer in lengthto dimension Y of the expander than to the unmodified hypotenuse.

As best shown in FIG. 1 in this particular embodiment, expander 122 hasa depth dimension Z that is less than that of first and seconddimensions Y, X. Expander 122 of the present embodiment has a fixedshape during movement from initial insertion position I to finaldeployed position F within implant 100.

As shown in FIGS. 22A, 22B, and 23, blocker 121 may also take the formof a trailing wall that articulates or hinges to the inside of implant100. The trailing wall may be left open during insertion of implant 100so as to trail behind the upper and lower members. The trailing walldoes not protrude outside of a projection rearward of the circumferenceof implant 100. Once implant 100 is implanted into position, thetrailing wall is rotated about one of its ends and pushed into positionand locked into place. This may occur by having the trailing wallcontact an inclined plane that leads up to a notch into which thetrailing wall locks into place. The trailing wall itself may also haveat least one opening in it to permit the further loading offusion-promoting materials into implant 100.

While modified hypotenuse MH is illustrated as being between arcs 144 inthis preferred embodiment, the configuration of expander 122 to formmodified hypotenuse MH can take many forms, such that those junctionsare relieved so as to have the desired lesser dimension therebetween,including arcs, chamfers, a series of angled surfaces, or any othershape so long as the modified hypotenuse MH is sufficiently reduced indimension to function for the intended purpose according to the presentteaching.

An embodiment of the present invention where modified hypotenuse MH isslightly greater than height Y offers the advantage of an over-centereffect that locks expander 122 into place. In this instance, onceexpander 122 rotates past the diagonal of the modified hypotenuse MH,more force would be required to rotate it back from the final deployedposition to its insertion position than in an embodiment where modifiedhypotenuse MH is equal to or less than height Y. Preferably, expander122 offers a surgeon multiple sensory advantages including: the tactilefeel of expander 122 going over center and locking into place; thevisual of the handle of a tool rotating expander 122 such that the toolhandle goes from perpendicular to parallel, the reverse, or other, tothe disc space into place; and auditory from the sound of expander 122snapping into place.

Each of upper and lower surfaces 136, 138 of expander 122 of the presentembodiment lie generally in a plane and are generally parallel to oneanother. For any implant it is anticipated that a physician may be ableto select from a series of blockers or expanders allowing for varyingthe increase in the implant height. Side surfaces 140 and upper andlower surfaces 136, 138 are oriented so as to substantially form aparallelogram. Any of a number of configurations for the expander forincreasing the height of the implant is possible, based on the teachingsof the present application and such configurations as would be known toone of skill in the art are anticipated within the scope of the presentinvention.

The implant may preferably have an overlapping step-cut wall junctionbetween upper and power members 102, 106 which offers the advantage ofincreasing the lateral rigidity of implant 100 holding the implant inthe closed first position until expanded, and to the extent desiredretaining the fusion-promoting materials within. The wall junction maybe either solid or perforated. As best shown in FIG. 1, upper member 102in one embodiment of the preferred invention has interior walls 146extending from each side of arcuate portion 104 toward lower member 106.Interior wall 146 is aligned parallel to longitudinal axis L of implant100. Lower member 106 has an interior-contacting surface 148 adapted tocontact or receive interior wall 146.

In a preferred embodiment, upper and lower members 102, 106 arearticulated to one another so one of the respective ends of upper andlower members 102, 106 remain articulated while the other of therespective ends of upper and lower members 102, 106 are free to moveaway from one another. In a preferred embodiment the articulating meansis achieved without a third member such as an axle shaft passing throughthe implant. The articulating means preferably is formed into theimplant walls themselves in such a way that the two implant halves maybe articulated when the halves are at 90 degrees to each other and thenthe halves are moved toward each other for insertion into theimplantation space in the spine. The two halves are closed much like thecover of a book. The halves are locked together such thatdisarticulation will not occur when the implant is assembled for use.Any of a number of ways of articulating or joining upper and lowermembers 102, 106 is possible.

As best shown in FIG. 1 in this embodiment, upper and lower members 102,106 of the present embodiment have a pivot point between adjacent distalends 126 or leading ends 150 of upper and lower members 102, 106. Thepivot point in the present embodiment is at the end of implant 100opposite expander 122. The pivot point of the present embodimentoperates as a hinge or axle 152 but is formed out of the wallsthemselves so as to preferably not intrude into the implant interior orhollow or to block access thereto. Hinge 152 includes a projection 154extending radially from each side of arcuate portion 108 of lower member106 and a slotted bracket 156 extending from each side of arcuateportion 104 of upper member 102 for engaging projection 154. Brackets156 and projections 154 are configured such that engagement occurs whenupper and lower members 102, 106 are substantially perpendicular to oneanother. Brackets 156 and projections 154 are configured so as not todisengage within a range of movement of upper and lower members 102, 106that would occur when the implant is in use either during insertion orresulting from the expansion in height of implant 100.

As best shown in FIG. 11, interior wall 146 of upper member 102 of thepresent embodiment is unexposed when implant 100 is in initial insertionposition 1. As shown in FIG. 12C, when implant 100 is in the expandedposition F, implant 100 has a shape such that each of arcuate portions104, 108 of upper and lower members 102, 106 are separated by at least aportion of interior wall 146, which in this position has an exposedside. The exposed side of the present embodiment is smooth and flat.

As best shown in FIG. 8, a cap 158 having an exterior surface 160 and aninterior surface 162 is used to close leading end 150 of implant 100.Interior surface 162 of cap 158 has spaced slots 164 about itscircumference to facilitate a snap fit between cap 158 and implant 100.Cap 158 and implant 100 can of course be adapted for either or both endsof implant 100.

As discussed above, implant 100 has a leading end 150 and a trailing end126. One of the ends preferably has a tool-engaging portion. Thistool-engaging portion is adapted to engage an insertion tool that holdsand rotates implant 100 into position. The tool-engaging configurationmay be an opening, and more particularly an opening that is along thelongitudinal axis of the implant to facilitate the use of an insertiontool that rotates implant 100 into an inserted position. Of course, thetool-engaging portion need not be an opening. A hole or a blind hole,threaded or otherwise, is preferred in another embodiment. In anotherpreferred embodiment the opening preferably is a threaded slot thatfunctions to cooperatively engage and disengage a tool for use ininserting implant 100. The opening either alone on the proximal end ofimplant 100 or in conjunction with other openings on the proximal endfunction to hold fusion-promoting material in implant 100 whilepermitting vascular access and bone growth through the opening oropenings.

Implants of the present invention may have an end adapted tocooperatively engage an implant driver. The anterior approach implantmay have a leading end, trailing end, or both ends that are adapted toengage a cap. One of the purposes for that cap includes restricting thepassage of fusion-promoting substances so that they remain loaded withinthe implant. Another purpose of the cap may be to add structural supportto the implant. The cap may be solid or it may have openingstherethrough. Any such openings could allow for the loaded material tostay within the implant while providing for vascular access to allow forthe ingrowth of blood vessels and the growth of bone through the end ofthe implant.

For a posterior approach implant, the cap may be on either or both ends.The trailing end of the implant in a posterior approach implant hasdirect exposure to the spinal canal where the spinal cord and nerveroots are located. A cap on a posterior approach implant may be for thepurpose of sealing off the spinal canal from the fusion-promotingsubstances contained in the hollow interior of the implant so that nobone grows into the canal. Further, the present invention implant may beused in combination with chemical substances and/or compounds applied atthe trailing end of the implant to inhibit scar formation, and the capmay be of benefit in shielding the fusion-promoting substances containedin the implant from these scar formation inhibiting chemicals andcompounds. It may also be for the purposes identified herein used inassociation with the leading end cap of an anterior approach implant.

Shown in FIGS. 14-16, in accordance with the present invention, asembodied and broadly described herein, is a second embodiment of anexpandable threaded artificial interbody spinal fusion implant 200 forposterior insertion across a disc space D between two adjacent vertebralbodies V of a human spine. Threaded implant 200 of the present inventionincludes an upper member 202 having an arcuate portion 204 adapted forplacement toward and at least in part within the upper of the adjacentvertebral bodies V and a lower member 206 having an arcuate portion 208adapted for placement toward and at least in part within the lower ofthe adjacent vertebral bodies V.

As shown in FIG. 14, implant 200 may be angled or tapered so as toconverge from trailing end to leading end when in the collapsed positionfor insertion into the spine. The taper on implant 200 may facilitateits insertion. Alternatively, as shown in FIG. 14A, the implant of thepresent invention may be angled or tapered so as to diverge fromtrailing end to leading end when in the collapsed position for insertioninto the spine. For an implant with an angle that diverges for trailingend to leading end, the leading end may have a chamfer or otherconfiguration to reduce the size of the leading end to facilitateinsertion of the implant into the spine.

Implant 200 in FIGS. 14 and 15 is shown being implanted into the spinefrom the posterior aspect with expander 222 on the distal end 226 orleading end 250 of implant 200. While anterior and posterior aspectapproaches have been illustrated herein, the present invention is notlimited to these illustrated approaches. In particular, but not limitedthereto, the threaded implant of the present invention also may be usedin threaded implants for insertion from the translateral aspect of thespine as disclosed by Michelson in U.S. Pat. No. 5,860,973, which isincorporated herein by reference.

As best shown in FIG. 16, tracks 232, 234 of upper and lower members202, 206 of the second embodiment have a cooperating surface 266 andexpander 222 has a corresponding cooperating surface 268 that contactscooperating surface 266 of tracks 232, 234 to orient expander 222 in apredetermined location. The cooperating surfaces orient expander 222within implant 200 such that the axis of rotation of expander 222 isparallel to the longitudinal axis of implant 200 and more particularlycenter expander 222 within implant 200 such that the axis of rotation ofexpander 222 coincides with longitudinal axis L of implant 200.

Tracks 232, 234 include sides 270 having cooperating surface 266 andexpander 222 has corresponding cooperating surface 268 used to orientexpander 122 in a predetermined location. Cooperating surface 266 ofside 270 is a detent and corresponding cooperating surface 268 ofexpander 222 is a projection. The projection preferably projects awayfrom expander 222 in a direction parallel to the longitudinal axis ofimplant 200. The detent and the projection preferably center expander222 within implant 200 such that the axis of rotation of expander 222coincides with the longitudinal axis of implant 200.

Shown in FIGS. 17-19, in accordance with the present invention, asembodied and broadly described herein, is a third embodiment of anexpandable threaded artificial interbody spinal fusion implant 300 forinsertion across a disc space D between two adjacent vertebral bodies Vof a human spine. Threaded implant 300 of the present invention includesan upper member 302 having an arcuate portion 304 for orientation towardthe upper of adjacent vertebral bodies V and a lower member 306 havingan arcuate portion 308 for orientation toward the lower of the adjacentvertebral bodies V.

Implant 300 of the present embodiment may include any of the variousfeatures disclosed in association with implant 100 and implant 200disclosed herein. Implant 300 further includes a side surface 372contoured to cooperatively receive another implant. See U.S. Pat. No.5,593,409 by Michelson for a discussion of the advantages associatedwith placing implants in side-by-side contact.

Another aspect of implant 300 is that its upper and lower members 302,306 have screw holes 374 passing therethrough adapted to receive a screw378 passing from the interior of implant 300 into adjacent vertebralbodies V to anchor implant 300 to an adjacent vertebral body V.

The articulation may be of one of two general types, examples of whichare each herein disclosed. As shown in previously described embodimentsof the present invention, the articulation may allow rotation about thearticulation. A second type of articulation allows for both rotation andexpansion at the point of articulation. An example of this is shown inFIG. 19, where a peg and hook design is utilized. While in this exampleboth functions, that is rotation or pivoting, and captured or limitedexpansion with a fixed end point or stop, occur at the same location.Alternatively, and without departing from the teachings of the presentinvention, those functions can be divided. By way of example only, andnot limitation, expansion can be allowed and controlled by aninterlocking wall design, as shown by the interlocking members in thealternative embodiments of FIGS. 20 and 21. Various other structuralfeatures as would be obvious to one of ordinary skill in the art afterthe teachings herein can similarly be employed.

A fixed end point for the implant expansion is preferred for the properfunctioning of the opposed bone screws. A purpose of the opposed bonescrews is to rigidly secure the implant within the vertebral segment. Afurther purpose is to pull each of the adjacent vertebral bodies towardthe implant and towards each other so as to have a construct resistantto the deleterious effects of vertebral rocking as may otherwise occurwith spinal flexion and extension absent such restraint. If thearticulation device captured the upper and lower members together, as inthe embodiments of FIG. 1-16, by closely encircling a post then theimplant could not expand at that location. So the coupling mechanism ofFIG. 19 permits the upper and lower members to remain articulated,permits the implant to expand, and permits the screws to pull againstthe implant and each other, in opposite directions and to pull the bonestoward each other. The optional extended slot and peg configuration onthe right-hand side of FIG. 19 illustrated in dashed image lines is notneeded to hold the implant together.

In accordance with this embodiment of the present invention, a secondexpander may be located at least in part between the upper and lowermembers for moving at least a portion of the upper and lower membersaway from one another to increase the height of the implant defined bythe maximum distance between the arcuate portions of the upper and lowermembers. All of the features described herein for the expander may alsobe applicable to the second expander. Additionally, the second expandermay be located proximate an end of the implant opposite the otherexpander, thereby providing an implant capable of being expanded at bothends of implant. The increased height of the implant resulting frommoving the two expanders may be the constant or varied along the lengthof the implant according to the desired configuration of the implant.

The expandable threaded spinal fusion implant may be made of artificialor naturally occurring materials suitable for implantation in the humanspine. The implant can comprise bone including, but not limited to,cortical bone. The implant can also be formed of material other thanbone, such as metal including, but not limited to, titanium and itsalloys or ASTM material, surgical grade plastics, plastic composites,ceramics, or other materials suitable for use as a threaded spinalfusion implant. The plastics may be bioresorbable. The threaded spinalfusion implant of the present invention can further be formed of bonegrowth promoting materials, including but not limited to, bonemorphogenetic proteins, hydroxyapatite, and genes coding for theproduction of bone. The threaded implant can be treated with a bonegrowth promoting substance, can be a source of osteogenesis, or can beat least in part bioabsorbable. The threaded implant of the presentinvention can be formed of a porous material.

The expandable threaded spinal fusion implant of the present inventionmay be coated with, comprised of, be used in combination with, or have ahollow for containing bone growth promoting materials, including but notlimited to, bone morphogenetic proteins, hydroxyapatite, and genescoding for the production of bone. The threaded spinal fusion implant ofthe present invention can be formed of a material that intrinsicallyparticipates in the growth of bone from one of adjacent vertebral bodiesV to the other of adjacent vertebral bodies V.

While various embodiments of the present invention are presented by wayof example only and not limitation, common to each of them, is that theexpandable threaded spinal fusion implant for insertion across discspace D between two adjacent vertebral bodies V of a human spine has anupper member having an arcuate portion adapted for placement toward andat least in part within the upper of the adjacent vertebral bodies V.The implant also has a lower member having an arcuate portion adaptedfor placement toward and at least in part within the lower of theadjacent vertebral bodies V. The arcuate portions of the upper and lowermembers have at least one opening. The openings of the upper and lowermembers are in communication with one another to permit for the growthof bone from vertebral body V to adjacent vertebral body V through theimplant. At least a portion of a thread for engaging adjacent vertebralbodies V is on the exterior of each of the opposed arcuate portions ofthe upper and lower members. A blocker in the form of an expanderpreferably is located proximate at least one of the ends to hold atleast a portion of the upper and lower members apart from one another toincrease the implant height.

There is disclosed in the above description and the drawings implants,which fully and effectively accomplish the objectives of this invention.However, it will be apparent that variations and modifications of thedisclosed embodiments may be made without departing from the principlesof the invention or the scope of the appended claims.

1. A threaded interbody spinal fusion implant for at least in partrotational insertion across a disc space between two adjacent vertebralbodies of a spine, said implant comprising: an upper member having aportion being at least in part arcuate adapted for placement toward andat least in part within one of the adjacent vertebral bodies, said uppermember having at least one opening adapted to communicate with one ofthe adjacent vertebral bodies, said upper member having a proximal endand a distal end; a lower member having a portion being at least in partarcuate adapted for placement toward and at least in part within theother of the adjacent vertebral bodies, said lower member having atleast one opening adapted to communicate with the other of the adjacentvertebral bodies, said openings of said upper and lower members being incommunication with one another and adapted for permitting for the growthof bone from adjacent vertebral body to adjacent vertebral body throughsaid implant and being sufficiently sized and located to allow forinterbody spinal fusion through said implant, said lower member having aproximal end and a distal end corresponding to said proximal end andsaid distal end of said upper member, respectively, and a length betweensaid proximal and distal ends, said upper and lower members articulatingtherebetween adjacent one of said proximal ends and said distal ends ofsaid upper and lower members and allowing for expansion of the height ofsaid implant, said upper and lower members having a first positionrelative to one another allowing for a collapsed implant height and asecond position relative to one another allowing for an increasedheight, said arcuate portions of said upper and lower members in thefirst position being angled to one another over a substantial portion ofthe length of said implant and forming at least a portion of afrusto-conical shape along the length of said implant; at least aportion of a helical thread formed on the exterior of each of saidopposed arcuate portions of said upper and lower members for penetrablyengaging the adjacent vertebral bodies and to facilitate securing saidimplant into the spine by at least in part rotating said implant aboutthe longitudinal axis of said implant; and at least one blocker adaptedto cooperatively engage and hold at least a portion of said upper andlower members apart so as to maintain the increased height of saidimplant and resist the collapse of said implant to the collapsed implantheight when said implant is in a final deployed position.
 2. Thethreaded implant of claim 1, further comprising a hollow defined betweensaid upper and lower members in communication with said openings in eachof said upper and lower members, said hollow being adapted to receivefusion-promoting substances.
 3. The threaded implant of claim 2, whereinsaid hollow has a width that is unobstructed by any mechanism for movingsaid blocker.
 4. The threaded implant of claim 2, further comprising asecond hollow between said upper and lower members located between saidblocker and said end of said implant proximate said blocker.
 5. Thethreaded implant of claim 3, wherein said implant has a constant widthin both the collapsed height and the increased height.
 6. The threadedimplant of claim 3, wherein said blocker is located at least in partbetween said upper and lower members.
 7. The threaded implant of claim3, wherein said blocker is located at a predetermined location along thelength of said implant and remains at the predetermined location intransitioning said implant from said first position to said secondposition.
 8. The threaded implant of claim 3, wherein said blocker islocated proximate at least one of said ends of said upper and lowermembers.
 9. The threaded implant of claim 3, wherein said blocker isadapted to cooperatively engage a tool used to move said blocker from aninitial position to a final position to increase the height of saidimplant, said tool not being a part of said implant and being removedfrom said implant after moving said blocker into the final position. 10.The threaded implant of claim 3, wherein said implant has a width andsaid blocker has a width less than the width of said implant.
 11. Thethreaded implant of claim 3, wherein said implant has side walls andsaid blocker does not contact said side walls when said implant is inthe final deployed position.
 12. The threaded implant of claim 3,wherein each of said upper and lower members are adapted to cooperatewith and to fixedly locate said blocker.
 13. The threaded implant ofclaim 12, wherein each of said upper and lower members have a trackconfigured to permit said blocker to seat therein.
 14. The threadedimplant of claim 13, wherein at least one of said tracks and saidblocker are adapted to cooperate with each other to center said blockeralong a longitudinal axis of said implant.
 15. The threaded implant ofclaim 3, wherein said blocker moves said arcuate portions of said upperand lower members from a first angled orientation to a second angledorientation relative to one another.
 16. The threaded implant of claim3, further comprising a second blocker located between said upper andlower members for holding at least a portion of the upper and lowermembers apart where said second blocker is located.
 17. The threadedimplant of claim 3, wherein said blocker is an expander adapted toexpand said implant from a first collapsed height to a second expandedheight when moved from a first to a second position.
 18. The threadedimplant of claim 17, wherein said implant has a longitudinal axis andsaid expander rotates in a plane generally perpendicular to thelongitudinal axis of said implant to increase the height of saidimplant.
 19. The threaded implant of claim 17, wherein said expander islocated along the length of said implant.
 20. The threaded implant ofclaim 17, wherein said expander is located proximate said proximal endsof said upper and lower members.
 21. The threaded implant of claim 17,wherein said expander is located proximate said distal ends of saidupper and lower members.
 22. The threaded implant of claim 17, furthercomprising a hollow defined between said upper and lower members incommunication with said openings in each of said upper and lowermembers, said hollow being adapted to receive fusion-promotingsubstances, said hollow being substantially unobstructed by saidexpander extending along a substantial portion of the length of saidhollow so as to permit growth of bone from adjacent vertebral body toadjacent vertebral body through said implant.
 23. The threaded implantof claim 17, wherein said expander remains in the same location alongthe longitudinal axis of the implant when rotated.
 24. The threadedimplant of claim 17, wherein said expander is located at a predeterminedlocation along the length of said implant and remains so located intransitioning said implant from the first position to the secondposition.
 25. The threaded implant of claim 17, wherein said expander isadapted to cooperatively engage a tool used to move said expander froman initial position to a final position to increase the height of saidimplant, said tool not being a part of said implant and being removedfrom said implant after moving said expander into the final position.26. The threaded implant of claim 17, wherein said expander is adaptedto cooperatively engage a tool that rotates about an axis parallel tothe longitudinal axis of said implant to rotate said expander toincrease the height of said implant.
 27. The threaded implant of claim26, wherein said expander rotates in a plane perpendicular to thelongitudinal axis of said implant to increase the height of saidimplant.
 28. The threaded implant of claim 27, wherein said expanderremains in the same location along the longitudinal axis of the implantwhen rotated.
 29. The threaded implant of claim 17, wherein saidexpander moves said arcuate portions of said upper and lower membersfrom an angled orientation to an angled orientation relative to oneanother.
 30. The threaded implant of claim 17, wherein each of saidupper and lower members are adapted to cooperate with said expander. 31.The threaded implant of claim 30, wherein each of said upper and lowermembers have a track configured to permit said expander to rotatetherein.
 32. The threaded implant of claim 31, wherein said trackspermit said expander to move from side to side within said track. 33.The threaded implant of claim 31, wherein said track of said uppermember and said track of said lower member are in the same plane. 34.The threaded implant of claim 31, wherein said track of said uppermember and said track of said lower member are parallel to one another.35. The threaded implant of claim 31, where said track of said uppermember and said track of said lower member are in a plane perpendicularto the longitudinal axis of said implant.
 36. The threaded implant ofclaim 17, wherein said upper and lower members structurally cooperatewith said expander so as to keep said expander located within saidimplant.
 37. The threaded implant of claim 31, wherein at least one ofsaid tracks of said upper and lower members has a cooperating surface,said expander having a corresponding cooperating surface that contactssaid cooperating surface of said at least one track to orient saidexpander in a predetermined location.
 38. The threaded implant of claim37, wherein said cooperating surfaces orient said expander within saidimplant such that the axis of rotation of said expander is parallel withthe longitudinal axis of said implant.
 39. The threaded implant of claim38, wherein said cooperating surfaces center said expander within saidimplant such that the axis of rotation of said expander coincides withthe longitudinal axis of said implant.
 40. The threaded implant of claim3, wherein said upper and lower members are configured to cooperate withone another so as to stop said upper and lower members from being movedapart from one another more than a predetermined distance.
 41. Thethreaded implant of claim 30, wherein said upper and lower members areadapted to cooperate with said expander so as to center said expanderwithin a cross section of the upper and lower members.
 42. The threadedimplant of claim 31, wherein at least one of said tracks of said upperand lower members includes at least one side having a cooperatingsurface, said expander having a corresponding cooperating surface thatcontacts said cooperating surface of said at least one side to orientsaid expander in a predetermined location.
 43. The threaded implant ofclaim 42, wherein said cooperating surface of said at least one side isa detent and said corresponding cooperating surface of said expander isa projection.
 44. The threaded implant of claim 43, wherein said detentand said projection center said expander within said implant such thatthe axis of rotation of said expander coincides with the longitudinalaxis of said implant.
 45. The threaded implant of claim 17, wherein saidexpander has a first height corresponding to the height of said expanderwhen said implant is initially inserted into the spine, said expanderhaving a second height corresponding to the height of said expander whensaid expander is moved into a final deployed position to increase theheight of said implant, said second height being greater than said firstheight.
 46. The threaded implant of claim 17, wherein said expander hasan upper surface, a lower surface, and side surfaces as defined whensaid expander is positioned to increase the height of said implant, saidside surfaces intersecting said upper and said lower surfaces at twodiametrically opposed junctions.
 47. The threaded implant of claim 46,wherein said two diametrically opposed junctions are a pair ofdiametrically opposed corners and a pair of diametrically opposed arcs.48. The threaded implant of claim 46, wherein each of said upper andlower surfaces lie generally in a plane.
 49. The threaded implant ofclaim 46, wherein said upper and lower surfaces are generally parallelto one another.
 50. The threaded implant of claim 46, wherein said sidesurfaces and said upper and lower surfaces are oriented to substantiallyform a parallelogram.
 51. The threaded implant of claim 45, wherein thedifference between said first height and said second height of saidexpander approximates the difference in height of said implant betweensaid first position and said second position as measured proximate thelocation of said expander.
 52. The threaded implant of claim 47, whereinsaid two diametrically opposed arcs are each of the same radius.
 53. Thethreaded implant of claim 52, wherein the distance across said twodiametrically opposed arcs generally approximates the distance betweensaid upper and lower surfaces of said expander.
 54. The threaded implantof claim 47, wherein said two diametrically opposed corners form a90-degree angle.
 55. The threaded implant of claim 17, wherein saidexpander has a depth dimension less than that of said first and secondheight of said expander.
 56. The threaded implant of claim 55, whereinsaid expander has a fixed shape during movement from an initialinsertion position to a final deployed position within said implant. 57.The threaded implant of claim 17, further comprising a second expanderlocated between said upper and lower members for moving at least aportion of the upper and lower members away from one another to increasethe maximum height of said implant where said second expander islocated.
 58. The threaded implant of claim 57, wherein said secondexpander rotates to increase the height of said implant.
 59. Thethreaded implant of claim 57, wherein said second expander is locatedproximate an end of said implant opposite said expander.
 60. Thethreaded implant of claim 57, wherein said implant has a longitudinalaxis and said second expander rotates in a plane perpendicular to thelongitudinal axis of said implant to increase the height of saidimplant.
 61. The threaded implant of claim 59, wherein said hollow issubstantially unobstructed by said second expander extending along asubstantial portion of the length of said hollow so as to permit growthof bone from adjacent vertebral body to adjacent vertebral body throughsaid implant.
 62. The threaded implant of claim 59, wherein said secondexpander remains in the same location along the longitudinal axis of theimplant when rotated.
 63. The threaded implant of claim 57, wherein saidsecond expander is located proximate one of the proximal end and thedistal end of said upper and lower members.
 64. The threaded implant ofclaim 63, wherein said hollow is unobstructed by said second expanderextending along a substantial portion of the length of said hollow topermit growth of bone from adjacent vertebral body to adjacent vertebralbody through said implant.
 65. The threaded implant of claim 63, furthercomprising a second hollow between said upper and lower member locatedbetween said second expander and said end of said implant proximate saidsecond expander.
 66. The threaded implant of claim 57, wherein each ofsaid upper and lower members have a track within which said secondexpander rotates.
 67. The threaded implant of claim 66, wherein saidtrack is configured to permit said second expander to rotate therein andthen to move from side to side within said track.
 68. The threadedimplant of claim 57, wherein said second expander has a first heightcorresponding to the height of said second expander when said implant isinitially inserted into the spine, said second expander having a secondheight corresponding to the height of said second expander when saidsecond expander is moved into a final deployed position to increase theheight of said implant, said second height being greater than said firstheight.
 69. The threaded implant of claim 57, wherein said secondexpander has an upper surface, a lower surface, and side surfaces asdefined when said second expander is positioned to increase the heightof said implant, and said side surfaces intersecting said upper and saidlower surfaces at two diametrically opposed junctions.
 70. The threadedimplant of claim 69, wherein the difference between said first heightand said second height of said second expander approximates thedifference in height of said implant between said first position andsaid second position as measured proximate the location of said secondexpander.
 71. The threaded implant of claim 3, wherein said upper andlower members have walls contacting one another.
 72. The threadedimplant of claim 71, wherein said walls are aligned parallel with thelongitudinal axis of said implant.
 73. The threaded implant of claim 71,wherein said walls are at least in part overlapping.
 74. The threadedimplant of claim 3, wherein said upper and lower members have arotational articulation therebetween adjacent one of said proximal endand said distal end of said upper and lower members.
 75. The threadedimplant of claim 74, wherein said rotational articulation is at one ofsaid proximal end and said distal end of said upper and lower membersopposite said blocker.
 76. The threaded implant of claim 74, whereinsaid rotational articulation allows for expansion.
 77. The threadedimplant of claim 76, wherein said rotational articulation allows forlimited expansion.
 78. The threaded implant of claim 74, wherein saidrotational articulation is formed by said upper and lower membersinterdigitating so as to cooperatively engage.
 79. The threaded implantof claim 78, wherein said rotational articulation is configured suchthat engagement occurs when said upper and lower members aresubstantially perpendicular to one another.
 80. The threaded implant ofclaim 79, wherein said rotational articulation is configured to remainengaged within a range of movement of said upper and lower membersresulting from positioning said implant in the second position.
 81. Thethreaded implant of claim 3, wherein one of said upper and lower membershas an interior wall, which is unexposed, extending therefrom toward theother of said upper and lower members when said implant is in an initialinsertion position, and when said implant is in a final position saidimplant has a shape such that each of said arcuate portions of saidupper and lower members are separated by at least a portion of saidinterior wall, which now has an exposed side.
 82. The threaded implantof claim 81, wherein said upper and lower members have side walls forengaging each other.
 83. The threaded implant of claim 82, wherein saidside walls of said upper and lower members are at least partiallyoverlapping walls.
 84. The threaded implant of claim 81, wherein saidarcuate portions of said upper and lower members form an angularorientation relative to one another when said implant is in the finalposition.
 85. The threaded implant of claim 81, wherein said arcuateportions of said upper and lower members when said implant is in theinitial insertion position form a frusto-conical shape.
 86. The threadedimplant of claim 3, wherein said implant has an interior, at least oneof said upper and lower members has a screw hole passing therethroughadapted to receive a screw passing from said interior of said implantinto one of the adjacent vertebral bodies.
 87. The threaded implant ofclaim 86, wherein each of said upper and lower members has at least onescrew hole passing therethrough adapted to receive a screw passing fromsaid interior of said implant into the adjacent vertebral body incontact with each of said upper and lower members respectively.
 88. Thethreaded implant of claim 86, further comprising at least one screwadapted to pass from said interior of said implant through said screwhole and into the adjacent vertebral body to anchor said implant to theadjacent vertebral body.
 89. The threaded implant of claim 3, whereinsaid implant has a side surface when in a final position that iscontoured to cooperate with another implant.
 90. The threaded implant ofclaim 89, wherein said implant and said cooperating other implant have acombined width therebetween less than the combined height of saidimplant and said cooperating other implant.
 91. The threaded implant ofclaim 3, further comprising a cap for closing one of said proximal endand said distal end of said upper and lower members, said cap having anexterior surface and an interior surface.
 92. The threaded implant ofclaim 91, wherein said interior surface of said cap has spaced slotsabout its circumference to facilitate a snap fit of said cap into saidimplant.
 93. The threaded implant of claim 3, wherein said implantcomprises an artificial material other than bone.
 94. The threadedimplant of claim 3, wherein said implant is made of an artificialmaterial that is stronger than bone.
 95. The threaded implant of claim3, wherein said implant is made of an artificial material that is harderthan bone.
 96. The threaded implant of claim 3, wherein said implantcomprises bone.
 97. The threaded implant of claim 96, wherein said boneincludes cortical bone.
 98. The threaded implant of claim 3, whereinsaid implant comprises bone growth promoting material.
 99. The threadedimplant of claim 98, wherein said bone growth promoting material isselected from one of bone morphogenetic protein, hydroxyapatite, andgenes coding for the production of bone.
 100. The threaded implant ofclaim 3, wherein said implant is treated with a bone growth promotingsubstance.
 101. The threaded implant of claim 3, wherein said implant isa source of osteogenesis.
 102. The threaded implant of claim 3, whereinsaid implant is at least in part bioabsorbable.
 103. The threadedimplant of claim 3, wherein said implant comprises metal.
 104. Thethreaded implant of claim 103, wherein said metal is ASTM materialsuitable for use said threaded spinal fusion implant.
 105. The threadedimplant of claim 103, wherein said metal includes titanium.
 106. Thethreaded implant of claim 3, wherein said implant comprises a plasticmaterial.
 107. The threaded implant of claim 3, wherein said implantcomprises a ceramic material.
 108. The threaded implant of claim 3,wherein said implant is formed of a porous material.
 109. The threadedimplant of claim 3, wherein said implant is formed of a material thatintrinsically participates in the growth of bone from adjacent vertebralbody to adjacent vertebral body through said implant.
 110. The threadedimplant of claim 3, wherein said implant has an interior surface and ahollow defined therein, said hollow being capable of containing bonegrowth promoting material.
 111. The threaded implant of claim 110,wherein said bone growth promoting material is selected from one of bonemorphogenetic protein, hydroxyapatite, and genes coding for theproduction of bone.
 112. The threaded implant of claim 3, wherein saidat least one opening is adapted to retain fusion-promoting materials.113. The threaded implant of claim 3, wherein at least a portion of saidimplant is treated to promote bone ingrowth between said implant andsaid adjacent vertebral bodies.
 114. The threaded implant of claim 3, incombination with a chemical substance to inhibit scar formation. 115.The threaded implant of claim 3, wherein said blocker is an expanderhaving an external thread, each of said upper and lower members having athreaded converging portion adapted to cooperate with said externalthread of said expander to expand said implant from a first collapsedheight to a second expanded height when said expander is rotated from afirst to a second position.
 116. A threaded interbody spinal fusionimplant for at least in part rotational insertion across a disc spacebetween two adjacent vertebral bodies of a spine, said implantcomprising: an upper member having a portion being at least in partarcuate adapted for placement toward and at least in part within one ofthe adjacent vertebral bodies, said upper member having at least oneopening adapted to communicate with one of the adjacent vertebralbodies, said upper member having a proximal end and a distal end; alower member having a portion being at least in part arcuate adapted forplacement toward and at least in part within the other of the adjacentvertebral bodies, said lower member having at least one opening adaptedto communicate with the other of the adjacent vertebral bodies, saidopenings of said upper and lower members being in communication with oneanother and adapted for permitting for the growth of bone from adjacentvertebral body to adjacent vertebral body through said implant and beingsufficiently sized and located to allow for interbody spinal fusionthrough said implant, said lower member having a proximal end and adistal end corresponding to said proximal end and said distal end ofsaid upper member, respectively, and a length between said proximal anddistal ends, said upper and lower members articulating therebetweenadjacent one of said proximal ends and said distal ends of said upperand lower members and allowing for expansion of the height of saidimplant, said upper and lower members having a first position relativeto one another allowing for a collapsed implant height and a secondposition relative to one another allowing for an increased height, saidarcuate portions of said upper and lower members in the first positionbeing angled to one another over a substantial portion of the length ofsaid implant and forming at least a portion of a frusto-conical shapealong the length of said implant; at least a portion of a helical threadformed on the exterior of each of said opposed arcuate portions of saidupper and lower members for penetrably engaging the adjacent vertebralbodies and to facilitate securing said implant into the spine by atleast in part rotating said implant about the longitudinal axis of saidimplant; and a blocker pivotally attached to one of said upper and lowermembers proximate one of said proximal and distal ends and being adaptedto pivot into cooperative engagement with another of said one of saidupper and lower members, said blocker being adapted to hold at least aportion of said upper and lower members apart so as to maintain theincreased height of said implant and resist the collapse of said implantto the collapsed implant height when said implant is in a final deployedposition, said implant having a width and said blocker having a widthless than the width of said implant.